Grey dagger, Acronicta psi, Apatele psi
The grey dagger (right) is common throughout Europe and the British isles, and found in most habitats especially woodlands, hedgerows and gardens. There is one generation a year, though there may be 2 generations in the south.
Eggs are laid singly on the foodplant (see caterpillar) leaves in July or August, and hatch in a week.
The caterpillar (see left) is blue/grey with a yellow stripe down its back, and white below the spiracles, red spots above, a black head, a spike on its back just after the true legs, and another spike or hump just before the last pair of prolegs. Foodplants include birch, alder, hawthorn, blackthorn, plum, pear, apple, and many others. Length is up to 38 mm. They feed from August until October.
They pupate in a silk cocoon in the cracks of bark, in rotten wood or in the soil.
Adults emerge the following year in June. Adult length at rest is 17 - 20 mm, and the wingspan is 30 - 42 mm. It is very similar to the Dark dagger, Acronicta tridens.